And to their surprise, they found that emotional stress isn’t the only cause or even the main cause. And sometimes, the effects can kill people even years later.

The medical name for the syndrome is takotsubo cardiomyopathy or stress cardiomyopathy. It was first formally described in 1990, and it’s a type of heart rhythm disorder.

Mostly seen in elderly women, it’s named after a Japanese word for “octopus pot” because of the distinctive way the heart changes shape as part of the symptoms. It causes chest pain, shortness of breath, and, sometimes, fainting.

The theory is that something triggers the brain to signal the adrenal glands, which in turn send stress hormones that make the heart go haywire.

It looks like a heart attack on an electrocardiogram or EKG, but it’s not, and patients rarely have blocked arteries.

It’s often blamed when couples die within days or even hours of one another. And there’s no clear guidance for how to treat it.

An international team of researchers looked at the records of more than 1,700 patients diagnosed with the condition in nine countries between 1998 and 2014. Nearly ninety percent were women.

They wanted to see what really causes the syndrome, whether it kills patients often, and how best to treat them.

They compared 455 patients with the broken heart syndrome to 455 similar people with acute coronary syndrome, which produces similar symptoms, and who had suffered heart attacks or who had chest pain known as unstable angina.

Physical triggers were more common than emotional triggers, the researchers found. These included acute respiratory failure, surgery, broken bones or brain injury and caused 36 percent of the cases.

Emotional triggers caused about 27 percent of cases and included grief, panic, fights and anger or frustration. But in more than 28 percent of cases, there was no obvious trigger, Dr. Christian Templin of University Hospital Zurich in Switzerland and colleagues reported in the New England Journal of Medicine.

Nearly 56 percent of the patients with takotsubo cardiomyopathy had a history of either a neurological disorder or a psychiatric disorder. Only about a quarter of patients with acute coronary syndrome did.

Men were more likely to die than women. About 13 percent of the men with takotsubo syndrome died each year after diagnosis, compared to 5 percent of men with acute coronary syndrome.

Seven percent of the patients had a heart attack, stroke or other major “event” within the first month of being admitted to the hospital. Men had a higher risk than women. They found patients had a higher risk of complications than previously believed, and said doctors need to keep an eye out for them.

Is there anything that can help? Blood-pressure-lowering drugs such as beta-blockers didn’t, but others called ACE inhibitors did, they found.

Whatever it truly is, it’s real, they said. “Takotsubo cardiomyopathy should be considered to be an acute heart failure syndrome,” they wrote.